The present invention relates to stair case construction and more particularly relates to a stair module which co operates with similar or identical stair modules to form a stair case. The invention has been primarily developed in order to produce a relatively light weight stair module which allows assembly and dismantling of stair cases which are particularly useful for temporary stair casing as is often used on building sites. Although the invention to be described herein has other applications it will be primarily described with reference to its application in the construction of temporary stairs for use in the construction industry. However, it should be appreciated that the invention is not limited to this particular mode and field of use and can be employed in more permanent stairways. The invention further relates to a module for construction of stairs which can be used in any application in which stairways are required for permanent or temporary purposes such as but not limited to temporary event structures including outdoor structures and grandstands for concerts and the like.